Charge Calibration in the Si Tracker test-beam Mathieu Trocmé Summer Student 2003 Supervisor: Helge Voss

28 August 2003

Testbeam Analysis, Charge Calibration - Mathieu Trocmé

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The LHCb Experiment


2 Si strip detectors:

Inner Tracker (High Occupancy)

Trigger Tracker

28 August 2003

Testbeam Analysis, Charge Calibration - Mathieu Trocmé

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Si Strip Detector Read out

Ionisation

Collection

Capacitance
=> Noise
28 August 2003

Testbeam Analysis, Charge Calibration - Mathieu Trocmé

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Experimental Setup (1/2) Goal: Enough signal for long ladders ? Which thickness ? 5 different ladders (modules) • 3 CMS sensors • 3 Glast sensors • 1 LHCb sensor • 2 LHCb sensors • 3 LHCb sensors

28 August 2003

(500 µm thick) (410 µm thick) (320 µm thick) (320 µm thick) (320 µm thick)

Testbeam Analysis, Charge Calibration - Mathieu Trocmé

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Experimental Setup (2/2) Different Regions within the LHCb sensors Charge Injection

Read Out ( Beetle Chips x3 )

Width=50 µm Width=60 µm Width=70 µm Width=70 µm Width=80 µm

/ / / / /

Pitch=198.0 µm Pitch=198.0 µm Pitch=198.0 µm Pitch=237.5 µm Pitch=237.5 µm

Pitch (p) Width (w)

‘w/p’ influences the total strip Capacitance 28 August 2003

Testbeam Analysis, Charge Calibration - Mathieu Trocmé

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Charge Calibration (1/5) 1 ADC Count

≡

N electrons ?

ADC Count Measurement for each injected charge (250mV, 350mV, 450mV)

28 August 2003

Testbeam Analysis, Charge Calibration - Mathieu Trocmé

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Charge Calibration (2/5) Raw Data




= Pedestals

2 Methods: - “Event by Event” - “Average”

28 August 2003

Testbeam Analysis, Charge Calibration - Mathieu Trocmé

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Charge Calibration (3/5) ADC Count measurement: Distribution over all the events and over each single pulsed strip

ADC Range (8 bits)

Beetle with different Gain (in the readout chain) 28 August 2003

Testbeam Analysis, Charge Calibration - Mathieu Trocmé

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Charge Calibration (4/5) Noise

Offset despite Pedestals subtraction

Slope

Front End Measurement

ADC(Noise) ENC =

28 August 2003

Testbeam Analysis, Charge Calibration - Mathieu Trocmé

Slope 9

Charge Calibration (5/5) Charge on neighbouring channels ?

≠

Charge Injection

28 August 2003

Different Time Structure

Testbeam Analysis, Charge Calibration - Mathieu Trocmé

‘Real’ Data

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Conclusion • Experimental Setup: . Signal OK with 3 sensors (400-500 µm thick )

• Charge Calibration: . Hardware problem (Grounding effects ?) . Beetle Internal test pulse . Try other pedestals

28 August 2003

Testbeam Analysis, Charge Calibration - Mathieu Trocmé

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